Organic light emitting display device and method of fabricating the same

ABSTRACT

An organic light emitting display device and a method of fabricating the same are provided. The organic light emitting display device includes a substrate having first, second and third pixel regions, and an upper substrate facing the substrate. The thicknesses of regions of the upper substrate respectively facing the first, second and third pixel regions are different from each other. The thicknesses of the regions of the upper substrate facing the pixel regions are formed different from each other, such that the organic light emitting display device having an optimal or improved optical resonance structure can be provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2005-0021967, filed Mar. 16, 2005, the entire contentof which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light emitting displaydevice and a method of fabricating the same, and more particularly, toan organic light emitting display device having an optimal (or improved)resonance structure and a method of fabricating the same.

2. Description of the Related Art

In general, an organic light emitting display device having thin filmtransistors for driving pixel circuits is an active matrix lightemitting display device having a fast response speed as well as a wideviewing angle and excellent contrast, so that it has attracted attentionas a next generation display device.

The organic light emitting display device is classified as either aninorganic electroluminescent (EL) display device or an organic ELdisplay device according to materials used for forming an emittinglayer. The organic EL display device has excellent luminance, drivevoltage, and response speed characteristics, and displays many colorscompared to the inorganic EL display device.

In addition, pixel regions defined by a plurality of scan lines and aplurality of data lines formed in a direction perpendicular to thedirection of the scan lines may display red, green, and blue colors, sothat the organic light emitting display device may constitute afull-color flat panel display device.

FIG. 1 is a schematic cross-sectional view of a conventional organiclight emitting display device.

Referring to FIG. 1, the organic light emitting display device generallyhas a substrate 110 and an upper substrate 120 formed above thesubstrate 110. The upper substrate 120 covers (or encapsulates) thesubstrate 110 using an adhesive 130 or the like.

A red color pixel region (R), a green color pixel region (G), and a bluecolor pixel region (B) are disposed on the substrate 110 to display red,green, and blue colors, respectively.

A first electrode layer, an emitting layer, and a second electrodelayer, which each have a predetermined pattern, are formed on thesubstrate 110 in each of the pixel regions. Several layers constitutingeach of the pixel regions are not shown in FIG. 1 for simplicity ofdescription.

A hole injection layer and a hole transport layer may be formed as acommon layer on the entire surface of the substrate having the firstelectrode layer. An emitting material corresponding to each of the pixelregions is stacked on the hole transport layer to form R, G, and Bemitting layers.

A hole blocking layer, an electron transport layer, and an electroninjection layer are sequentially formed on the entire surface of thesubstrate if necessary, and a second electrode layer is formed on theelectron injection layer. In this case, the hole injection layer, thehole transport layer, the emitting layer, the hole block layer, theelectron transport layer, and the electron injection layer are organicthin layers formed of an organic compound.

However, in a case of the full color organic light emitting displaydevice, a difference between luminous efficiencies per pixel, i.e., percolor, occurs. That is, the luminous efficiency of the green coloremitting material is superior to those of the red and blue coloremitting materials. In addition, the luminous efficiency of the redcolor emitting material is superior to that of the blue color emittingmaterial.

Accordingly, there have been many attempts to obtain maximum efficiencyand luminance by controlling the thickness of the organic thin layers inthe related art. For example, Japanese Laid-Open Patent Publication No.1992-137485 discloses a technique for enhancing the luminous efficiencyby setting the thickness of an electron transport layer in a range of 30to 60 nm in a structure sequentially having a positive electrode, a holetransport layer, an emitting layer, the electron transport layer, and anegative electrode.

In addition, Japanese Laid-Open Patent Publication No. 1992-328295discloses a technique for substantially increasing the luminance byadjusting the thickness of an electron transport layer when lightemitting from an emitting layer interferes with light reflected from anegative electrode. In addition, Japanese Laid-Open Patent PublicationNo. 1995-240277 discloses an organic light emitting display device forenhancing luminance and color purity of blue emission by controlling anoptical layer thickness.

Such organic light emitting display devices set the optical thickness tobe different from each other per color in order to enhance theluminance. However, it is difficult to entirely change the process percolor to form a different optical thickness per color in a massproduction process.

SUMMARY OF THE INVENTION

The present invention, therefore, provides an organic light emittingdisplay having an optimal or improved resonance structure per each ofRGB pixels and a method of fabricating the same. The RGB pixels may alsobe referred to as RGB sub-pixels since all three of the RGB pixels areneeded to display a full color pixel.

In an exemplary embodiment according to the present invention, anorganic light emitting display device includes: a substrate having afirst pixel region, a second pixel region, and a third pixel region; andan upper substrate facing the substrate. In this case, thicknesses ofregions of the upper substrate respectively facing the first, second andthird pixel regions are different from each other.

In another exemplary embodiment according to the present invention, amethod of fabricating an organic light emitting display device includes:forming a substrate having a first pixel region, a second pixel region,and a third pixel region; and disposing an upper substrate over thesubstrate, and encapsulating the substrate with the upper substrate. Inthis case, thicknesses of regions of the upper substrate respectivelyfacing the first, second and third pixel regions are different from eachother.

The upper substrate may be formed by etching or sandblasting a surfacefacing the substrate, or may be formed by coating the surface facing thesubstrate.

A difference between the thicknesses of the regions of the uppersubstrate facing the first and second pixel regions, respectively, maybe substantially equal to a difference between optical wavelengths oflights emitted at the first and second pixel regions, and a differencebetween the thicknesses of the regions of the upper substrate facing thesecond and third pixel regions, respectively, may be substantially equalto a difference between optical wavelengths of lights emitted at thesecond and third pixel regions.

The first, second and third pixel regions may display different colorsfrom each other, and each of the first, second and third pixel regionsmay display one color among red, green, and blue colors. In particular,the first pixel region may display a blue color, the second pixel regionmay display a green color, and the third pixel region may display a redcolor.

The upper substrate may be formed of a transparent material, and inparticular, may be formed of glass or plastic.

Each of the pixel regions disposed on the substrate may include a firstelectrode layer formed on the substrate, an organic layer having atleast an emitting layer formed on the first electrode layer, and asecond electrode layer formed on the organic layer.

The first electrode layer may include a reflective electrode, and thesecond electrode layer may include a transparent electrode.

The first electrode layer may include a transparent electrode having areflective layer, and the second electrode layer may include atransmissive metal electrode. The transmissive metal electrode may beone selected from the group consisting of Ca, Ca/Ag, and Mg/Ag.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will be describedin reference to certain exemplary embodiments thereof with reference tothe attached drawings in which:

FIG. 1 is a schematic cross-sectional view of a conventional organiclight emitting display device;

FIG. 2 is a schematic cross-sectional view illustrating an organic lightemitting display device and a method of fabricating the same accordingto a first embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a pixel region formed on asubstrate of an organic light emitting display device according to anembodiment of the present invention; and

FIG. 4 is a schematic cross-sectional view illustrating an organic lightemitting display device and a method of fabricating the same accordingto a second embodiment of the present invention.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which certain exemplaryembodiments of the invention are shown. This invention may, however, beembodied in different forms and should not be construed as limited tothe embodiments set forth herein. Like reference numerals designate likeelements throughout the specification.

FIG. 2 is a schematic cross-sectional view illustrating an organic lightemitting display device and a method of fabricating the same accordingto a first embodiment of the present invention, and FIG. 3 is aschematic cross-sectional view of a pixel region formed on a substrateof an organic light emitting display device according to an embodimentof the present invention.

Referring to FIG. 2, the organic light emitting display device accordingto the first embodiment of the present invention includes a substrate110 and an upper substrate 220 formed on the substrate 110.

The substrate 110 has a first pixel region 111, a second pixel region112, and a third pixel region 113.

The first pixel region 111, the second pixel region 112, and the thirdpixel region 113 may display different colors from each other, and eachof the pixel regions may display one color among red, green, and bluecolors. For example, the third pixel region displays a blue color whenthe first pixel region corresponds to a red color and the second pixelregion corresponds to a green color, and the third pixel region displaysa red color when the first pixel region corresponds to a green color andthe second pixel region corresponds to a blue color. Alternatively,similar combinations of colors may be used to define the pixel regions.

In one embodiment, the first pixel region 111 displays a blue color (B),the second pixel region 112 displays a green color (G), and the thirdpixel region 113 displays a red color (R) because the thickness ofregions of the upper substrate 220 facing (or corresponding to) each ofthe pixel regions increases in order of the first pixel region 111, thesecond pixel region 112, and the third pixel region 113. A detaileddescription thereof will be given later.

By way of example, a transparent insulating substrate such as a glass orplastic substrate may be used as the substrate.

Referring to FIG. 3, a first electrode layer 311 is formed in each pixelregion.

The first electrode layer 311 may be formed of a reflective electrode.The reflective electrode may be formed of one or more selected from Al,an Al alloy, a double reflective layer such as Indium Tin Oxide (ITO),Indium Zinc Oxide (IZO) or the like formed on Ag, or a triple layer ofAg and ITO or the like. In addition, the first electrode layer 311 maybe formed of a transparent electrode having a reflective layer.

A pixel defining layer 312 is formed on the first electrode layer 311,and then patterned to form an opening in an emitting region. An organicinsulating layer such as BCB, acrylic resin or the like may be used forthe pixel defining layer 312.

Subsequently, an emitting layer 313 is formed on the first electrodelayer 311. That is, a first emitting material, a second emittingmaterial, or a third emitting material is patterned to form the emittinglayer 313 as one of first, second or third emitting layers on the firstelectrode layer 311. Each of the emitting materials may display onecolor among red, green, and blue colors, and may include an organicemitting material.

In one embodiment, the red color emitting layer is formed of aphosphorescent material including Carbazole BiPhenyl (CBP) or mCP as ahost material, and at least one of PIQIr(acac)(bis(1-phenylisoquinoline)acetylacetonate iridium), PQIr(acac)(bis(1-phenylquinoline)acetylacetonate iridium), tris(1-phenylquinoline)iridium (PQIr) or octaethylporphyrin platinum (PtOEP) as a dopantmaterial. The red color emitting layer may be formed of a fluorescentmaterial such as PBD:Eu(DBM)3(Phen) or Perylene.

In one embodiment, the green color emitting layer is formed of aphosphorescent material including CBP or mCP as a host material, andIr(ppy)3 (fac tris(2-phenylpyridine) iridium) as a dopant material.

In addition, the green color emitting layer may be formed of afluorescent material such as Alq3(tris(8-hydroxyquinolino)aluminum).

In one embodiment, the blue color emitting layer is formed of afluorescent material including one material selected from DPVBi,spiro-DPVBi, spiro-6P, distyryl benzene (DSB), distyryl arylene (DSA),poly(9,9-di-n-octyl-2,7-fluorene) (PFO) polymer, and poly-paraphenylenevinylene (PPV) polymer. When the blue color emitting layer is formed ofa phosphorescent material, the optical characteristics may be unstable,so that it is formed of the above-described fluorescent materials.

These emitting layers may be formed by a typical method such as a LaserInduced Thermal Imaging (LITI) method, an inkjet method, or anevaporation method.

A second electrode layer 314 is formed on the emitting layer 313. Thesecond electrode layer 314 may be formed of a transparent electrode or atransmissive metal electrode. In particular, the transmissive metalelectrode may be formed of one of Ca, Ca/Ag, or Mg/Ag.

At least one layer of a hole injection layer or a hole transport layermay be formed under the emitting layer 313 in the exemplary organiclight emitting display device of the present invention, and at least onelayer of a hole blocking layer, an electron transport layer, or anelectron injection layer may be further formed on the emitting layer313.

Referring back to FIGS. 2 and 3, the upper substrate 220 is formed abovethe substrate 110, and covers (or encapsulates) the substrate 110 usingan adhesive 130.

A space (or gap) 140 between the substrate 110 and the upper substrate220 may be filled with air, and a protection layer may be formed toprotect elements formed on the substrate 110. In this case, the space140 between the substrate 110 and the upper substrate 220 is not takeninto account when an optical path to be described later is appliedthereto.

In one embodiment, the upper substrate 220 is formed of a transparentmaterial, and in particular, glass or plastic.

In this case, thicknesses of the regions of the upper substrate 220facing the first pixel region 111, the second pixel region 112, and thethird pixel region 113 are different from each other. The thicknesses ofthe regions of the upper substrate 220 facing the pixel regions are madedifferent from each other in the described embodiment in order to havean optimal or improved resonance structure for the pixel regions.

In more detail, wavelength ranges when the red, green, and blue colorshave the respective maximum intensities are different from each other.For example, a wavelength range corresponds to 460 nm at the time of themaximum intensity of the blue color, 520 nm at the time of the maximumintensity of the green color, and 630 nm at the time of the maximumintensity of the red color. In this case, if an optical path lengthbetween the emitting layer and the upper substrate 220 (a of the firstpixel region 111), that is, an optical thickness of the upper substrate220, is the same for each color, a difference between movement distancesof the light according to the wavelength occurs so that an opticalcharacteristic may not be optimally obtained.

Accordingly, the difference between the wavelength ranges at the time ofthe maximum intensities of the respective colors is taken into account,so that the optical path lengths between the emitting layer and theupper substrate 220, i.e., the optical thicknesses of regions of theupper substrate 220 that correspond to different color pixel regions aremade different from each other in the described embodiment to obtain anoptimal (or improved) optical resonance structure.

According to the described embodiment, in order to have the optimal (orimproved) optical resonance structure, the optical path differencebetween the emitting layer and the upper substrate 220 of two pixelregions adjacent to each other, i.e., the difference between opticalthicknesses of two regions of the upper substrate 220, is madesubstantially equal to a wavelength difference when colors of the twopixel regions have the maximum intensities.

For example, when a difference between the wavelength when the color ofthe first pixel region 111 has the maximum intensity and the wavelengthwhen the color of the second pixel region 112 has the maximum intensityis x, a difference between the optical path length between the emittinglayer of the first pixel region 111 and the upper substrate 220, and theoptical path length between the emitting layer of the second pixelregion 112 and the upper substrate 220, becomes x. That is, when theoptical path length of the first pixel region 111 corresponds to a, theoptical path length of the second pixel region 112 corresponds to a+x.Accordingly, the difference of the optical thicknesses of the uppersubstrate 220 facing the first and second pixel regions 111 and 112,becomes x.

Accordingly, when the difference between the optical thicknesses of theregions of the upper substrate 220 respectively facing the first andsecond pixel regions 111 and 112 is made to be x, an optimal (orimproved) optical resonance structure may be obtained.

In a similar manner, when a wavelength difference when the colors of thesecond and third pixel regions 112 and 113 adjacent to each other havethe maximum intensities is y, a difference between the optical pathlength between the emitting layer of the second pixel region 112 and theupper substrate 220, and the optical path length between the emittinglayer of the third pixel region 113 and the upper substrate 220, becomesy, so that a difference between the optical thicknesses of the uppersubstrate 220 becomes y. Accordingly, when the difference of the opticalthicknesses of the upper substrate 220 facing the second and third pixelregions 112 and 113 is made to be y, an optimal (or improved) opticalresonance structure may be obtained.

As described above, when the first, second and third pixel regionsdisplay the blue, green, and red colors, respectively, the thickness ofthe region of the upper substrate 220 facing the first pixel region 111is the thinnest. And thicknesses of the corresponding regions of theupper substrate 220 are adjusted to be larger in an order of the secondpixel region and the third pixel region to obtain the optimal (orimproved) resonance structure.

Here, regions of the upper substrate 220 facing the first to third pixelregions may have different thicknesses from each other by using etchingor sandblast method.

The etching method may use dry etching or wet etching. The dry etchingis an etching method using a physical method by means of ion impact orusing a method of concurrently applying two phenomena like physical andchemical reactions as a chemical reaction of reactive materialsgenerated in plasma or as a chemical reaction carried out by ions,electrons, photons or the like. The wet etching is a method using achemical solution to remove the upper substrate 220 to comply with aphotoresist pattern, and dipping and spraying, or a mixed one thereofmay be employed for the wet etching as those skilled in the art wouldknow.

The sandblast method is a method which sprays or projects sand or pebbleto a structure using pressure or centrifugal force at a high speed toprocess a surface of the structure in a desired shape.

FIG. 4 is a schematic cross-sectional view illustrating an organic lightemitting display device and a method of fabricating the same inaccordance with a second embodiment of the present invention.

Referring to FIG. 4, the organic light emitting display device accordingto the second embodiment of the present invention includes a substrate110 and an upper substrate 320 formed above the substrate 110.

The substrate 110 has a first pixel region 111, a second pixel region112, and a third pixel region 113. The upper substrate 320 covers thesubstrate 110 using an adhesive 130.

Thicknesses of the regions of the upper substrate 320 facing the firstpixel region 111, the second pixel region 112, and the third pixelregion 113 are different from each other. The thicknesses of the uppersubstrate 320 facing the pixel regions are made different from eachother in the described embodiment of the present invention in order tohave an optimal (or improved) resonance structure, respectively.

Accordingly, optical path lengths between the emitting layer and theupper substrate 320, i.e., optical thicknesses of regions of the uppersubstrate 320, are made different from each other per color to obtain anoptimal (or improved) optical resonance structure.

In this case, the regions of the upper substrate 320 facing therespective first, second and third pixel regions are subjected tocoating to have different thicknesses from each other in the secondembodiment of the present invention.

The upper substrate 320 may use glass or plastic as a transparentmaterial, and the coating material used for the coating method may usethe same material as the upper substrate 320. That is, the glass orplastic may be used.

The organic light emitting display device and the method of fabricatingthe same for the second embodiment of FIG. 4 are substantially the sameas those of the first embodiment of FIG. 2, except as described above.

According to the described embodiments of the present invention,thicknesses of regions of an upper substrate facing respective pixelregions are made different from each other, so that an organic lightemitting display device having an optimal (or improved) opticalresonance structure may be provided.

Although the present invention has been described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that a variety of modifications and variations may bemade to the present invention without departing from the spirit or scopeof the present invention defined by the appended claims, and theirequivalents.

1. An organic light emitting display device, comprising: a substratehaving a first pixel region, a second pixel region, and a third pixelregion; and an upper substrate facing the substrate, wherein thicknessesof regions of the upper substrate respectively facing the first, secondand third pixel regions are different from each other.
 2. The organiclight emitting display device according to claim 1, wherein a differencebetween the thicknesses of the regions of the upper substrate facing thefirst and second pixel regions, respectively, is substantially equal toa difference between optical wavelengths of lights emitted at the firstand second pixel regions, and a difference between the thicknesses ofthe regions of the upper substrate facing the second and third pixelregions, respectively, is substantially equal to a difference betweenoptical wavelengths of lights emitted at the second and third pixelregions.
 3. The organic light emitting display device according to claim2, wherein the differences between the optical wavelengths of the lightsare differences between the optical wavelengths at their respectivemaximum intensities.
 4. The organic light emitting display deviceaccording to claim 1, wherein each of the pixel regions disposed on thesubstrate includes: a first electrode layer formed on the substrate; anorganic layer having at least an emitting layer formed on the firstelectrode layer; and a second electrode layer formed on the organiclayer.
 5. The organic light emitting display device according to claim4, wherein the first electrode layer comprises a reflective electrodeand the second electrode layer comprises a transparent electrode.
 6. Theorganic light emitting display device according to claim 4, wherein thefirst electrode layer comprises a transparent electrode having areflective layer and the second electrode layer comprises a transmissivemetal electrode which is one selected from the group consisting of Ca,Ca/Ag, and Mg/Ag.
 7. The organic light emitting display device accordingto claim 1, wherein the first, second and third pixel regionsrespectively correspond to blue, green and red pixel regions, whereinthe thickness of the region of the upper substrate facing the firstpixel region is less than the thickness of the region of the uppersubstrate facing the second pixel region, and wherein the thickness ofthe region of the upper substrate facing the second pixel region is lessthan the thickness of the region of the upper substrate facing the thirdpixel region.
 8. A method of fabricating an organic light emittingdisplay device, comprising: forming a substrate having a first pixelregion, a second pixel region, and a third pixel region; and disposingan upper substrate over the substrate, and encapsulating the substratewith the upper substrate, wherein thicknesses of regions of the uppersubstrate respectively facing the first, second and third pixel regionsare different from each other.
 9. The method according to claim 8,wherein a difference between the thicknesses of the regions of the uppersubstrate facing the first and second pixel regions, respectively, issubstantially equal to a difference between optical wavelengths oflights emitted at the first and second pixel regions, and a differencebetween the thicknesses of the regions of the upper substrate facing thesecond and third pixel regions, respectively, is substantially equal toa difference between optical wavelengths of lights emitted at the secondand third pixel regions.
 10. The method according to claim 9, whereinthe differences between the optical wavelengths of the lights aredifferences between the optical wavelengths at their respective maximumintensities.
 11. The method according to claim 8, further comprisingforming the upper substrate by etching or sandblasting a surface facingthe substrate.
 12. The method according to claim 11, wherein the first,second and third pixel regions respectively correspond to blue, greenand red pixel regions, and wherein said forming the upper substratecomprises: forming the region of the upper substrate facing the secondpixel region to have the thickness less than the thickness of the regionof the upper substrate facing the third pixel region; and forming theregion of the upper substrate facing the first pixel region to have thethickness less than the thickness of the region of the upper substratefacing the second pixel region.
 13. The method according to claim 8,further comprising forming the upper substrate by coating a surfacefacing the substrate.
 14. The method according to claim 13, wherein thefirst, second and third pixel regions respectively correspond to blue,green and red pixel regions, and wherein said forming the uppersubstrate comprises: forming the region of the upper substrate facingthe second pixel region to have the thickness greater than the thicknessof the region of the upper substrate facing the first pixel region; andforming the region of the upper substrate facing the third pixel regionto have the thickness greater than the thickness of the region of theupper substrate facing the second pixel region.
 15. The method accordingto claim 8, wherein each of the pixel regions formed on the substrateincludes: a first electrode layer formed on the substrate; an organiclayer having at least an emitting layer formed on the first electrodelayer; and a second electrode layer formed on the organic layer.
 16. Themethod according to claim 15, wherein the first electrode layercomprises a reflective electrode and the second electrode layercomprises a transparent electrode.
 17. The method according to claim 15,wherein the first electrode layer comprises a transparent electrodehaving a reflective layer and the second electrode layer comprises atransmissive metal electrode which is one selected from the groupconsisting of Ca, Ca/Ag, and Mg/Ag.